Touch systems are well known in the art and typically include a touch screen having a touch surface on which contacts are made using a pointer. Pointer contacts with the touch surface are detected and are used to generate corresponding output pointer position data representing areas of the touch surface where the pointer contacts are made. There are basically two general types of touch systems available and they can be broadly classified as “active” touch systems and “passive” touch systems.
Active touch systems allow a user to generate pointer position data by contacting the touch surface with a special pointer that usually requires some form of on-board power source, typically batteries. The special pointer emits signals such as infrared light, visible light, ultrasonic frequencies, electromagnetic frequencies, etc. that activate the touch surface.
Passive touch systems allow a user to generate pointer position data by contacting the touch surface with a passive pointer and do not require the use of special pointers in order to activate the touch surface. A passive pointer can be a finger, a cylinder of some material, or any other suitable object that can be used to contact some predetermined area of interest on the touch surface. Since special active pointers are not necessary in passive touch systems, battery power levels and/or pointer damage, theft, or pointer misplacement are of no concern to users. The detection of one or more points of contact with the touch screen or other display surfaces may be accomplished by a myriad of techniques.
United States Patent Application No. 20060279558 to Van Delden et al. discloses a display device having a touch screen 301. The touch screen comprises a first light guide 302, a second light guide 307, and a media 309 between the light guides for eliminating interference and reflections. A light source 308 is arranged to emit light 310 into the first light guide 302, where the light is normally confined within the first light guide by means of total internal reflections. The second light guide 307 is arranged at the exterior face of the first light guide 302. When a user of the display device establishes physical contact with the touch screen 301, light is extracted from the first light guide and directed towards light detecting means 303. The light detecting means 303 are arranged for relating a light detecting event to an input position on the touch screen 301, where user interaction occurred.
United States Patent Application No. 20060114244 to Saxena et al. discloses a touch input system including a light-emitting device, a bent light guide, and a light detector, whereby the light-emitting device emits light. The bent light guide receives the light emitted by the light-emitting device and guides the light to travel in a direction across a face of a display screen, where light detector detects the light. When an object interrupts transmission of light, the interruption is detected by an activated light detector opposite the light emitter transmitting light. This is illustrated by an object 17 interrupting light transmitted from one of light emitters 10 to light detectors 11, and interrupting light transmitted from one of light emitters 12 to light detectors 14.
United States Patent Application No. 20050104860 to McCreary et al. discloses a touchframe system including a plurality of light emitting elements and a plurality of light receiving elements positioned around the perimeter of a display area. Each of the light receiving elements in combination with a plurality of the light emitting elements form a zone of light beam paths. The number and positioning of receivers is sufficient to form a plurality of partially overlapping zone pairs. These zone pairs are arranged relative to the display area such that any touch event lies within at least two zone pairs. A processor monitors each of the zone pairs for blockage of at least one light beam path. Upon such blockage, the processor calculates the location of the touch event associated with the blockage based on the slopes and end points of at least two intersecting blocked light beam paths from a first zone pair and two intersecting blocked light beam paths from a second zone pair.
United States Patent Application No. 20040032401 to Nakazawa et al. discloses a substrate made of glass that serves both as a substrate for a touch panel and a front light. The substrate includes both the function of propagating an ultrasonic wave in order to detect a touched position, and propagating light emitted from a light source to guide the light toward a reflective-type liquid crystal display. In the case where an image on the liquid crystal display is made visible by external light, the external light that is transmitted through the substrate is reflected by the liquid crystal display and transmitted through the substrate to be emitted from the front face. In the case where the front light function is used, light which has been introduced into the substrate from the light source is reflected by the liquid crystal display and transmitted through the substrate to be emitted from the front face.
U.S. Pat. No. 7,002,555 to Jacobsen et al. discloses a display device having a touch sensor that consists of an electrochromic cell or a liquid crystal cell that is located between two transparent plates, a transparent cover plate, and a transparent support plate. A radiation source whose light enters the cover plate and illuminates it is arranged on at least one of the end faces of the transparent cover plate. At least one photodetector is mounted on the support plate.
U.S. Pat. No. 6,738,051 to Boyd et al. discloses a frontlit touch panel for use with a reflective light valve, where the panel comprises a front light guide having at least one light input face that supplies light to the guide, a viewing face, a light output face opposite the viewing face, and at least one component of a touch-sensitive transducer. The light output face includes a light extraction layer thereon having a substantially flat light exit face and contains buried reflective facets that extract supplied light from the guide through the light exit face. The touch panel can be used with a light source, a reflective light valve, and suitable control electronics to form a compact and efficient illuminated touch panel display assembly.
U.S. Pat. No. 4,710,760 to Kasday discloses a touch-sensitive device comprising a photoelastic screen having light reflecting edges and a unique light emitting/receiving module placed at two of the four corners of the screen, which advantageously determines the location at which a force is applied to the screen. Circularly and linearly polarized light focused into the photoelastic screen by the modules reflects off the edges of the screen and is returned to the modules where it is absorbed by a circular polarizer. The polarization of light passing through a point at which the screen is touched is changed thereby allowing these rays or signals to pass through each module's absorber. The location as well as the magnitude and direction of the force imparted to the screen by the touch is then determined from the changes in the signals that pass through the absorber.
It is therefore at least one object of the present invention to provide a novel system and method of detecting contact on a display screen.